Distillation of petroleum hydrocarbons



EJM. CLARK; u DlSTl-LLATION 0F PETROLEUM HYDROCARBONS.

APPLICATION FILED DEC. 14, 1M5- Patented Align 2 3, 1921 UNITED STATES PATENT OFFICE.

EDGAR M. CLARK, OF ALTON, ILLINOIS, ASSIGNOR TO STANDARD OIL COMPANY, OF

WRITING, INDIANA, A CORPORATION OF INDIANA.

DISTILLATION OF PETROLEUM HYDROCARBONS.

Application filed December i To all whom it may concern:

distillation employed being such that the stock charged into the still suffers that species of partial decomposition known as cracking. It is the particular object of the invention to provide an improved method of carrying on this cracking distillation, to the end that a larger yield of the desired lowboiling-point product may be had and the capacity and efficiency of the cracking apparatus increased.

The manner in which these objects are accomplished by the use of my invention will be more fully understood from the following I specification.

For the purpose of making my invention more clear, I will refer in the specification to the acompanying drawings in which there is shown a form of apparatus suitable for carrying out my process.

These drawings represent a side elevation of a still, condenser, and receiving drum, the

,showing being largely diagrammatic and the still and its furnace being sectioned.

Referring, more particularly, to the drawings, the numeral 10 designates, in general, the still which is used in my process. A furnace 11 is used for heating this still, the flue gases from the furnace escaping'througha stack 12. The vapors rising from the still are carried off by an upwardly inclined vapor pipe 13, known as a run-back or dephlegmator. At the upper end of this dephlegmator is mounted a fractional condenser 14 so arranged that its condensate returns to the dephlegmator and traverses the latter to reenter the still. From the upper portion of the fractional condenser 14 a va-' por line 15 leads to the condenser proper 16, which is shown as a pipe coil mounted in a water bath 17. A receiving drum for the distillate, designated 18, is mountedbelow the condenser 16 andis provided with a Specification of Letters Patent Patented Aug. 23, 1921.

14, 1915. Serial No. 66,702.

valved liquid draw-off 19 and a valved gasescape pipe 20, leading from its lower and upper ends, respectively.

The construction of the still and furnace designated generally 10 and 11 is shown in section in the drawing from which it will be seen that the still body which is of horizontal cylindrical form is supported upon columns 21 to lie above the furnace. From the shell or drum of the still, a pair of vertical trunks 22, 23, located at the rear and front of the shell respectively, lead downward and into the furnace proper. At the lower ends of these trunks are connected headers,

24, 25, between which extends a bank of tubes 26. These tubes are heated as by a grate 27 located in the front of the furnace, the hot gases of combustion being compelled to pass upwardly through the bank of tubes by the bridge wall 28, which extends through the tube bank and terminates just short of the crown 29. Leading downwardly from the rear end of the furnace is a vertical conduit 30 which is connected by the passage 31 with the stack 12. A gage glass 32 is applied to the rear end of the still.

The still and furnace construction above described is particularly desirable for operating under high pressure for the reason that the shell or drum itself is not subjected directly to the heat of the furnace and is therefore not subjectto the development of hot spots with their accompanying danger of explosion. The heating of the oil within the still is accomplished solely by the tubes 26 which, as shown, are arranged at a considerable angle to the horizontal whereby the heating of the oil results in a relatively rapid or forcible thermo-siphon circulation, which is sufficient to prevent the deposition of suspended carbon within the tubes them selves. A drain pipe 33 is tapped into the lower end of the header 25, that being the lowest point in the still.

The apparatus above described is particularly designed for use in carrying out the process of producing low-boiling-point hydrocarbons from hydrocarbons of higher boiling points, as broadly defined in the pat ent of \Villiam M. Burton, No. 1,049,667, and my own prior Patent No. 1,119,496.

In carrying out this process by the use of the apparatus I have just described, the

high-boiling-point stock which it is desired to convert into oil of a lower boiling point is introduced into the still 10 and is heated by means of the furnace 11.

As in the case of the Burton process referred to, the still, dephlegmator, and condenser form a single system the parts of which are in free communication. In the distillation process, therefore, the vapors generated in the still pass freely therefrom and to and through the condenser. From the latter the distillate and any uncondensed gases pass into the receiving drum, and the distillate there collects, to be drawn off either continuously or intermittently by the drawoif pipe 19, while the ases are permitted to discharge through t e valved pipe 20. By controlling the escape of these uncondensed gases, the entire system, including the still, may be brought up to any desired pressure and, the temperature of the still being proportionately raised, distillation may be continued under this pressure. Such is the general operation of the apparatus as so far described.

It is found in practice that when working with a stock of petroleum hydrocarbons composed of fractions. having boiling points ranging upwardly from 400 F. ,or there about, the distillation pressure being about 7 atmospheres and the temperature from 650 to 850 F. or thereabout, the character of the reactions takingplaceis such that the last 25 to 35 per cent. of the still charge is exceedingly refractory; in fact, it is considered uneconomical in large plants to further continue the distillation when the charge has been reduced to this volume. WVhen this point has been reached therefore, it is common to draw the furnace fires, drain, clean and inspect the still, and then re-charge with .a .fresh stock bringing this stock up to heat and distilling as before until about 65 to 7 5 per cent. has gone over, at which point the run is said to be finished. i

It is the particularobject of my invention to improve the process above defined to the end that the output of distillate at each run of the still may be considerably increased. I find that this may be accomplished by feeding either continuously or intermittently during the progress of the distilling operation a regulated quantity of fresh stock. I have found that under proper conditions I may add to the still during the runv of the when the additional stock. ,is charged into the upper endofthe dephlegmator 13 and is permltted to traverse the length ofthe latter before reaching the still. Inthe drawings- I have shown a supply pipe for introducing this additional charge, the pipe being provided with a cut-off valve or regulating valve 34 and a check valve 35. The pipe 33 will be connected with a supply of oil under pressure and by regulating this pressure or by regulating the valve 34 the feed may be nicely adjusted to give the best results. I have shown a drain pi )e 36 provided with a valve 37 tapped into the pipe 33, the drain pipe being adapted todraw off any tar which may collect at the foot of the air condenser 14 at the end of a run, or during the run.

In distilling petroleum hydrocarbons according to my process therefor, the following procedure will be employed:

The still 10 will be charged with the stock to be converted, the charge being suflicient to fill the still with the exception of a small vapor space at the upper surface of the liquid in the shell or drum. Fuel oil, gas oil, or the like residues boiling well above 400 F. and, in the instances mentioned, above-500 F. are the common stocks now emplo ed by me. The furnace 11 being fired t e still will bebrought up to its operating temperature. The gas escape pipe 20 will preferably be left open during the initial heating of the still so that any small quantity of water or low boiling point material in the stock may be driven off freely. As the temperature of the still approaches the boiling point of the stock, the gas valve of the pipe 20 will be closed, and the pres sure will then rise slowly, due to the formation or liberation of small quantities of incondensable gases, orthe fact that the condenser does not act to condense the vapors as fast as they are produced. In this connection it should be noted that in place of permitting the still to build up its own internal pressure, it is preferable to supply inert incondensable gas under pressure from an external source, as from another still which is in normal operation. This method of operation is described more fully in my prior Patent No. 1,129,034.

The internal pressure of the still and its connected dephlegmator and condenser having reached the desired point, for instance from 4 to 7 atmospheres or upward, the gas valve is properly regulated to maintain this pressure and, as the temperature of the still rises under continued firing, the distillation and cracking commence, as evidenced by the flow of the desired low-boiling-point products (i. e., crude gasolene) into the receiver from the condenser.

When this condition has been reached, the run is proceeded with until the liquid line in the still shows in the gage glass, and the temperature of the still contents has been appreciably increased. The feed of additional stock may now be commenced, the valve 34 being opened for this purpose. The

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rate of feed should be such as to maintain a fairly uniform liquid level within the still, as indicated by the gage glass. The fresh stock will therefore be supplied at about the rate of the collection of distillate in the receiver, although this figure is approximate only. As the distillation proceeds, the stock in the still remains about constant as to volume, but gradually becomes more refractory, and requires much higher temperatures for cracking. After upward of 200 per cent. oil the ori inal charge has been led into the still, the liquid body in the still has become so heavy, and the temperatures :tor craclring so high, and the proportion of fuel required to maintain these temperatures to distillate produced so great, that it is considered more economical to terminate the run than to continue. The valve 84 is theretore closed, the drain valve 37 opened, the tires drawn, and the still drained through the pipe 33, preparatory to cleaning and inspection.

By tending the additional stoclt into the top ot the dephlegmator instead ot directly into the still a highly important operative advantage is obtained in that the tresh stock is thoroughly treed ct any contained moistures, and in tact is fractionated and subjected to some craclring betore reaching the still proper. 'lthe disadvantages and dangers oil introducing raw stock into a highly heat-' ed still are thereby completely obviated.

l ll lin the toregoing specification l have set torth in considerable detail one method of carrying out my new process, and have also described the general arrangement and construction oil one term ot apparatus which it lind suitable tor use in the commercial operation. oil the same. lt is to he understood, however, that these details are illustrative only and tor the purpose of malring the invention more clear, and that l do not regard my invention as limited in any sense to these illustrated details, except in so tar as l have included such limitations within the terms oil the appended claims in which it is my intention to claim all novelty inherent in my invention. as broadly as is possible in view at the prior art.

What ll claim as new and desire to secure by Letters Patent is l. The process ot treating petroleum hydrocarbons oil relatively high boiling points to produce theret'rom hydrocarbons of lower boiling point which consists in distilling a liquid body of such high-hoiling-point stock under a pressure sullicient to eilect its decomposition, carrying oil the vapors of distillation While under the said pressure through a suitable unheated conduit leading away from the still, introducing fresh stock into the said conduit and causing it to traverse the latter and enter the still therethrough, and condensing and collecting the said vapors.

2. The'process of treating residual petroleum hydrocarbons oi the character of gas oil or fuel oil, to produce therefrom gasolenc hydrocarbons, which process consists in distilling a liquid body of such residual hydrocarbons under a pressure silt ficient to effect its decomposition, carrying oil the vapors oi distillation while under the said pressure through a suitable unheated conduit leading away from the still, introducing a fresh supply of said residual hydrocarbons into the said conduit and causing it to traverse the latter and enter the still therethrough, and condensing and collecting the said vapors.

3. The process of treating petroleum hy' drocarbons oi relatively high boiling points to produce therefrom hydrocarbons of lower boiling point, which consists in distilling a liquid body of such high-boiling-point stock under a pressure sutlicient to effect its decomposition, carrying otl the vapors of dis tillation while under the said pressure through a suitable unheated conduit leading away trom the still, condensing and collecting the said vapors, and introducing a fresh stoclr into the said conduit, the total quantity of additional stock so introduced being less than the quantity of distillates, and causing said tresh stoclr to traverse the said conduit and enter the still thercthrough.

l. 'lhe process of treating petroleum hydrocarbons having a boiling point of upward of rac l at atmospheric pressure, to produce therefrom hydrocarbons oi the gasolene series, which consists in distilling a liquid body of such high-boiling-point stock under a pressure of upward of t atmospheres, carrying oil the vapors ct distillation while under the said pressure through a suitable unheated conduit leading away trom the still, introducing tresh stock into the said conduit and causing it to traverse the latter and enter the still therethrough, and con densing and collecting the said vapors.

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